Knowledge Bank

The purpose of this research is to develop and fabricate an air powered variable stiffness soft robotic finger using primarily additive manufacturing. A soft finger is a type of manipulator typically constructed from compliant material that can deform to grip irregularly shaped objects. Due to their compliance, soft robots are safer for operation around humans and adaptable to a wide range of tasks. However, for similar reasons, they are unable to carry the higher loads rigid robots can handle. Variable stiffness technologies such as layer jamming can provide a solution to this problem, allowing the gripper to retain the benefits of a soft robot while increasing its payload capacity. Layer jamming uses overlapping sheets of plastic or paper attached at either end of a joint, which are then enclosed in an airtight envelope. Vacuum is applied to compress the layers, increasing the friction between them and thus the stiffness of the joint. In this research, a similar technique was applied, instead using positive pressure to compress the layers. Positive pressure allows for a higher force to be applied to the layers, increasing the performance potential over vacuum based jamming. Proof of concept soft fingers were manufactured using additive manufacturing to verify it as a manufacturing method. These designs were used to develop a set of best practices and settings for design and manufacture of 3D printed grippers. As there was little existing research on positive pressure layer jamming, numerous prototypes were printed to find an optimal design for integration with a soft finger. Once a suitable design was determined, a complete two finger gripper was manufactured and tested to analyze its performance. The design was then iterated to improve metrics such as actuation time, load capacity, and reliability. iii The techniques developed for additive gripper manufacturing proved successful and allowed for rapid design iteration. Four final fingers were produced and integrated into two grippers. One gripper was equipped with buttons for handheld use and a second was fitted to a UR5 Robot. These units were tested and successfully picked up a wide range of irregularly shaped and heavy objects. The individual finger was tested and found to have higher load capacity than similarly sized, commercially available soft fingers.